Reaction product of dialdehyde with starch ether in paper



United States Patent ice The present invention relates to improved paper and process 0 preparing same, and more particularly tomaking pape of excellent formation and increased dry strength either in the presence, or absence of one or more ,other materials (hereinafter defined) used in papermaking and the resulting paper product.

As is well known in the paperma-king art, papermaking comprises forming an aqueous slurry of a fibrous material,

passing the slurry onto a screen and thereby forming a sheet of the fibrous material and causing most of the water to be removed therefrom by gravity, and then pressing and drying the sheet to obtain the final paper product. Various materials have been added to the fibers to increase the dry strength of the final paper product. These materials are mixed with the fibers at any point prior to forming the wet lap on the screen of the papermaking machine. They are referred to in the art as internal additives as contrasted with materials which are applied to the surface of the paper after it is made in the form of a sheet.

Likewise, as is also Well known in the papermaking art, nonuniform formation of the sheet is a very serious problem. By nonuniform formation is meant an uneven distribution of fibers in the sheet. A number of difiiculties result from nonuniform formation. For example, nonuniform formation results in paper of substantially lower strength, nonuniform uptake of liquids, nonuniform passage of liquids through the paper, e.g. when used as oil filters, inefiicient use of the fibers, nonuniform thickness, nonuniform surface, poor printing, and poor appearance.

In accordance with the present invention, it has been found that paper of excellent formation and superior dry strength results from carrying out the process which comprises incorporating with the paperrnaking fibers, prior to forming the wet lap, the reaction product of a gelatinized cationic-nonionic starch ether and a dialdehyde. It has also been found in accordance with the present invention that said reaction products are good retention aids for paper additives, and that said reaction products serve the functions of substantially increasing the dry strength of paper and retaining paper additives either simultaneously or separately.

The term paper additives is used herein to include internal additives used in papermaking other than said dialdehyde-starch ether reaction products hereof, typical examples of which are fillers, colored pigments, dyes, sizes, fiber fines, wax emulsions, latex emulsions, etc.

The term cationic is used herein to mean that the starch compounds include a tertiary amino group. Typical examples of cationic-nonionic derivatives of starch applicable herein are cationic-hydroxyalkyl derivatives of starch having the formula:

wherein X is starch, R is selected from the group consisting of alkylene and hydroxyalkylene, R and R are each selected from the group consisting of alkyl, .aryl, aralkyl, cycloalkyl and heterocycloalkyl, and R is hy- 3,219,518 Patented Nov. 23, 1965 droxyalkyl. Of course, the R group may be attached to the same anhydroglucose unit as the radical or the R group may be attached to a different anhydroglucose unit.

Thus, representative of the starch ethers applicable in the present invention are diethylaminoethyl hydroxypropyl starch, diethylaminoethyl hydroxyethyl starch, dimet-hylaminoethyl hydroxypropyl starch, diethylaminopropyl hydroxypropyl starch, morpholinoethyl hydroxypropyl starch, and the like.

The starches which may be used as a starting material in preparing the starch ethers may be derived from any source including, e.g. wheat, corn, tapioca, potato, waxy maize, sago, rice. The starch may be of any form also, including e.g. raw starch, dextrinized starch, hydrolyzed starch, oxidized starch, and the like.

It is well known that starch, which in its natural state is in the form of discrete granules, will undergo gelatinization in the presence of water and sufiicient alkali. The phenomenon of gelatinization involves the swelling, rupture and disintegration of the starch granule, so that it will form a hydrated colloidal dispersion in water. Gelatinize-d starch is referred to in the art as cold water soluble or swellable. Actually, cold water swellable is more accurate since gelatinized starch does not dissolve in the true sense of the term. In fact, gelatinized starch hydrates so fast that a sticky gel forms over the surface of the particles, and a number of the particles cling together before they can be dispersed in the water. This causes lumping, sometimes referred to as agglomeration, and this in turn decreases the rate at which the starch can be dispersed in water. Lurnping also makes the starch more diflicult to disperse in water, i.e. more work is required to accomplish a given amount of dispersion in a specified time. The behavior of starch ethers in water approaches that of gelatinized starch with increase in D8. or MS. In contrast, ungelatinized starch granules will settle out of water suspension and may be filtered and dried, still retaining their original granule form. The problem of agglomeration is not involved with ungelatinized starch, nor is the problem serious with gelatinized starch ethers of BS. or MS. below about 0.10.

Since the starch ether-dialdehyde reaction products used in the present invention must be in a gelatinized state at the time of use, the starch ether reactants were prepared under such conditions that they gelatinized during preparation. Thus, in addition to giving excellent formation and increased dry strength, another advantage of the present invention is that the starch ether-dialdehyde reaction product has an improved dispersibility. That is, reaction of the dialdehydes with the starch ethers of the present invention substantially improves the dispersibility in water of the starch ethers. By improved dispersibility is meant an increased rate of dispersion which in turn gives an increased rate of solution in water.

The purpose of the following paragraph is to explain the use herein and in the prior art of the terms degree of substitution (D.S.) and MS.

There are three hydroxyl groups in each anhydroglucose unit in the starch molecule. D8. is the average number of hydroxyl groups substituted in the starch per anhydroglucose unit. MS. is the average number of moles of reactant combined with the starch per anhydroglucose unit. For the alkyl, carboxyalkyl, or acyl derivatives of starch, the D8. and MS. are same. For the hydroxyalkyl derivatives of starch, the MS. is generally greater than the D5. The reason for this is that each time a hydroxyalkyl group is introduced into the starch molecule, an additional hydroxyl group is formed which itself is capable of hydroxyalkylation. As a result of this, side chains of considerable length may form on the starch molecule. The M.S./D.S. ratio represents the average length of these side chains. Thus, from the foregoing it will be seen that the D8. of a starch derivative can be no higher than 3, whereas the M.S. may be considerably higher than 3, depending on the extent to which side chains are formed. Regarding the mixed ethers involved herein, the first value given is the aminoalkyl BS. and the second value given is the hydroxyalkyl M.S.

As disclosed hereinbefore the modified starch ether products applicable in the present invention are reaction products of a dialdehyde (e.g. glyoxal) and a cationicnonionic starch ether (e.g. a dialkylaminoalkyl hydroxyalkyl starch ether, including diethylaminoethyl hydroxypropyl starch). These reaction products and processes of preparing same are not per se a part of the present invention; they are disclosed and claimed in copending application Serial No. 268,564, entitled Starch Ethers and Process, filed on even date herewith in the name of Herbert C. Miller as inventor.

The following examples illustrate specific embodiments of the present invention but they are not intended to limit the invention beyond the scope of the claims appended hereto. In these examples and elsewhere herein percent and parts are by Weight unless otherwise indicated.

EXAMPLES 1-6 Solution or dispersion preparation of internal additive 5% aqueous solutions or dispersions of diethylaminoethyl hydroxypropyl starch (DEAE-HPS) and of glyoxalated diethylaminoethyl hydroxypropyl starch (G-DEAE- HPS), i.e. the reaction product of glyoxal and diethylpulp and thus giving paper of good ink resistance.

beaten in pH 7 tap water in a Noble and Wood cycle beater to a Schopper-Riegler freeness of 820 cc. Aliquots of the pulp slurry were diluted to 2.5% consistency and chemicals were added thereto in the following order:

(1) DEAE-HPS and G-DEAE-HPS (as said 5% aqueous solution above),

(2) 0.5% rosin size (by weight of dry pulp),

(3) 10% aqueous solution of papermakers alum (i.e. hydrated aluminum sulfate) to reduce the pH to 4.5.

The treated pulp was diluted to 0.5% consistency in a Noble and Wood proportioner using tap water containing 5 p.p.m. aluminum (as papermakers alum) and adjusted to pH 5 before pulp addition. Paper handsheets weighing lb./ream (ream is 500 24" x 36" sheets) were formed in a Noble and Wood sheet mold. The pulp was diluted to 0.05% consistency in the mold with tap;

water adjusted to pH 5. The sheets were pressed and dried in the conventional manner of the Noble and Wood handsheet system. The sheets were conditioned and tested in accordance with TAPPI (Technical Association of the Pulp and Paper Industry) standard methods, except for formation and ink resistance. Formation was determined by thorough visual examination by an experienced papermaker. In addition to giving good formation and substantially increased dry strength properties, the internal additive also served Well in retaining the rosin size on the Resistance to penetration of 10% lactic acid ink was determined using the procedure described in TAPPI, vol. 36, January 1953, pages 42-46. The ink resistance values in Table 1 hereinafter are given in seconds required for sample reflectance to drop to the 85% level.

Further details appear in Table 1 hereinafter.

TABLE I.ALUM AND ROSIN SIZED SYSTEM Internal Additive Mullen Burst, p.s.i. Tensile Strength, Ink Resistance Example 1b./in. Seconds N 0. Formation Type Amount 3 Actual Increase 4 Actual Increase 4 Actual Increase Control None Good 31. 5 15. 6 230 DEAE-HPS l 1 Poor 40. 0 8. 5 19. 7 4. 1 1, 020 790 G-DEAE-HPS 1 Good 42. 6 11. 1 20. 8 4. 7 1, 200 970 1 Diethylaminoethyl hydroxypropyl starch.

2 Diethylaminoethyl hydroxypropyl starch-glyoxal reaction product.

aminoethyl hydroxypropyl starch, were prepared by mixing in water at 25 C. ethyl hydroxypropyl starch used was the same and was in a gelatinized state when used in papermaking. The resulting G-DEAE-HPS solution was divided into two portions. One portion of the G-DEAE-HPS solution was used as internal additive and size retention aid in making alum and rosin-sized paper handsheets (Example 3, Table 1) to compare with alum and rosin-sized paper handsheets made with the resulting DEAE-HPS as internal additive and size retention aid (Example 2, Table 1) and also to compare with alum and rosin-sized paper handsheets made with no DEAE-I-IPS nor G-DEAE-HPS (Example 1, .Table 1).- The other portion of the G-DEAE-HPS solution was used in an alum free and unsized system as an internal additive in corrugating medium (Example 5, Table 2) to compare with corrugating medium made with no DEAE-HPS nor G-DEAE-HPS (Example 4, Table 2).

- EXAMPLES 1-3 Paper handsheet preparati0nAliim and rosin sized system i A 4.5% consistency unbleached kraft pulp slurry was In each case the 'diethylamino-- From a study of Examples 1-3 hereinbefore the following will be readily apparent. Good sheet formation is obtained without using either DEAE-HPS or G-DEAE- HPS, however the paper strength properties are substantially lower than desired. The desired increased paper strength properties are obtained by using a cationicnonionic starch ether which was gelatinized during its preparation (e.g. DEAE-HPS), however the sheet formation falls far below the quantity desired. The desired increased paper strength properties are obtained without sacrifice of sheet formation in accordance with the present invention by using the reaction product of a dialdehyde and a cationic-nonionic starch ether, said starch ether having been gelatinized during its preparation. In addition to giving good formation, and substantially increased dry strength properties, the glyoxal-diethylaminoethyl hydroxypropyl starch reaction product of the present invention also served well in retaining the rosin size on the pulp and thus giving paper of good ink resistance.

EXAMPLES 4 AND 5 Paper hands/tee! preparation Alum free and unsized system These handsheets were prepared in substantially the same manner as in Examples 13 hereinbefore except for the following differences. No size nor alum Was used. Tap water of pH 7 was used in the proportioner and sheet mold. Pulp consistencies were 0.5% and 0.05% in the proportioner and sheet mold, respectively. Handsheets weighing about 85 lb./ream (ream is 500 24" x 36" sheets) were formed and dried in the conventional manner. Crush resistance tests were conducted according to the Concora test method commonly used by corrugating medium manufacturers. A /z-in. x 6-in. strip cut from the handsheets was fluted in a standard Concora fiuter and mounted on a piece of masking tape. The specimen was then loaded in a standard Baldwin Universal Tester, using a loading rate of 1 inch per minute, until the flutes collapsed. (A discussion of the Concora test method and its development appears in TAPPI, vol. 39, page 88-A, September 1956.)

Further details are given in Table 2 hereinafter.

TABLE 2.ALUM FREE AND UNSIZED SYSTEM Internal Additive Concora Crush Example Resistance 3 Type Amount 2 Actual Increase 4 4 Control None 38.9 5 G-DEAE-HPS 0.88 44.9 6.0

l Diethylaminoethyl hydroxypropyl starch-glyoxal reaction product. Percent by weightof dry pulp.

3 Total load in pounds.

4 Based on untreated control (Example 4).

The chief objective in presenting the following Examples 6-13 is to show that the dialdehyde-starch ether reaction products of the present invention are also very good retention aids. The amount of paper filler used in the examples herein was 10% by weight of the pulp on a dry basis.

EXAMPLES 6-9 Solution 0r dispersion preparation of internal additive 5% aqueous solutions or dispersions of glyoxalated diethylaminoethyl hydroxypropyl starch G-DEAE-HPS i.e. the reaction product of diethylaminoethyl hydroxypropyl starch and glyoxal, were prepared by mixing in water at 25 C.

Paper handsheet preparationAlum and unsized systemClay and TiO fillers The slurry was diluted to 0.5% consistency in a Noble and Wood proportioner using tap water containing 5 p.p.m. aluminum (as papermakers alum) and then the slurry was adjusted to pH 4.5 G-DEAE-H'PS (to serve as retention aid) was added (as a 0.005% aqueous solution) to aliquots from the proportioner. Paper handsheets weighing 40 lb./rea-m (ream is 500 24" x 36' sheets) were formed in a Noble and Wood sheet mold. The pulp was diluted to 0.05% consistency in the mold with tap water adjusted to pH 5. The sheets were pressed and dried in the conventional manner of the Noble and Wood handsheet system. Then the percent retention of filler was determined by standard procedure from the ash contents of the paper handsheets.

6 Further details appear in Table 3 hereinafter.

TABLE 3.RETENTION EFFICIENCY-ALUM AND UNSIZED SYSTEM Retention Aid Percent Retention Example No.

Type Amount Clay 3 TlOz Added 3 Control None 18 I 40 G-DEAE-HPS 1 0.01 26 42 G-DEAE-IIPS 1 0.20 30 43 G-DEAE-HPS 1 0.40 36 45 1 Diethylamiuoethyl hydroxypropyl starch-glyoxal reaction product. 2 Percent by dry weight of pulp. I 3 Type used is known in trade as kaolin.

EXAMPLES 10-13 Solution 0r dispersion preparation of internal additive 5% aqueous solutions or dispersions of glyoxalated diethylaminoethyl hydroxypropyl starch (G-DEAE-HPS) were prepared by mixing in water at 25 C.

Paper handsheet preparation-Alum free and unsized systemClay and TiO fillers A 2.5% consistency bleached kraft pulp slurry was beaten in a Noble and Wood cycle heater to a Schopper- Riegler freeness of 600 cc. Aliquots of the pulp slurry were adjusted to pH 8.0. Then 10% filler was added to the pulp.

The slurry was diluted to 0.5 consistency in a Noble and Wood proportioner using tap water adjusted to pH 8.0. G-DEAE-HPS (to serve as retention aid) was added (as a 0.005% aqueous solution) to aliquots from the proportioner. Paper handsheets weighing 40 lb./ ream (ream is 500 24" x 36" sheets) were formed in a Noble and Wood sheet mold. The pulp was diluted to 0.05% con sistency in the mold with tap water adjusted to pH 8.0. The sheets were pressed and dried in the conventional manner of the Noble and Wood handsheet system. Then the percent retention of filler was determined by standard procedure from the ash contents of the paper handsheets.

Further details appear in Table 4 hereinafter.

TABLE 4.-RETENTION EFFICIENGY-ALUM FREE AND UNSIZED SYSTEM l Diethylaminoethyl hydroxypropyl starch-glyoxal reaction product. 3 Percent by dry weight of pulp. 3 Type used is known in trade as kaolin.

Experiments along the lines of the foregoing have also shown that the dialdehyde-starch ether reaction products of the present invention perform well to give paper of substantially increased dry strength and to retain paper additives, and that said reaction products perform these functions either simultaneously or separately.

As those skilled in the art will appreciate, many variations may be made in the foregoing examples within the scope of the present invention, some of which are set forth hereinafter.

Although for the sake of clarity and simplicity the present invention is described hereinbefore for the most part with reference to the reaction product of glyoxal and diethylaminoethyl hydroxypropyl starch ether, the present invention is applicable broadly to the use of the reaction products of dialdehydes and cationic-nonionic starch ethers. Applicable dialdehydes include, e.g. glyoxal, succinaldehyde, adipaldehyde, 2-hydroxy-adipaldehyde, glutaraldehyde. Likewise the present invention is applicable to cationic-nonionic starch ethers and more particularly those having the formula:

O-R4 X/ B2 \OR1N/ wherein X is starch, R is selected from the group consisting of alkylene and hydroxyalkylene, R and R are each selected from the group consisting of alkyl, aryl, aralkyl, cycloalkyl and heterocycloalkyl, and R is hydroxyalkyl. Of course, the R group may be attached to the same anhydroglucose unit as the R2 -R1N/ radical or the R group may be attached to a different anhydroglucose unit. Still more specifically preferred are the lower dialkylaminoalkyl hydroxyalkyl starches, e.g. diethylaminoethyl hydroxypropyl starch, diethylaminoethyl hydroxyethyl starch, dimethylaminoethyl hydroxypropyl starch, diethylamiuohydroxypropyl hydroxypropyl starch, etc.

' The diethylaminoethyl hydroxypropyl starch and the glyoxal-diethylaminoethyl hydroxypropyl starch reaction products used in the examples hereinbefore were prepared according to Examples 4 and 10, respectively, of said Herbert C. Miller copending application filed on even date herewith and further identified hereinbefore. However, as pointed out hereinbefore, the methods of preparing the starch ethers and the dialdehyde-starch ether reaction products applicable herein are not a part of the present invention and the present invention is not limited thereto or to the particular dialdehyde-starch ether reaction product disclosed in said Herbert C. Miller copending application.

The amount of dialdehyde-cationic-nonionic starch ether reaction products applicable in the present invention is not critical and may vary over a wide range, the amount being given herein by dry weight basis of the wood pulp or other cellulosic material being used as the papermaking furnish. However, usually a larger amount is used for increased dry strength than for retention. Also, from the standpoint of economy, normally one will not exceed about 10% (preferably 5%) for increased dry strength and about 8% (Preferably 3%) for retention. Amounts as low as 0.001% have given substantial retention results, and amounts as low as 0.1% have given substantial dry strength improvements, but these amounts are more apt to be at least 0.01% and at least 0.3%, respectively.

Although the present invention has been described in combination with rosin-alum size, it is applicable regardless of the type size or without size of any type. When making paper which is sized with rosin, alum and an acid pH are normally used. When rosin size is not used alum is normally omitted. Thus, some paper is made at neutral-to-alkaline pH with no size or any kind or with size (e.g. alkyl ketene dimer size known in the trade as Aquapel, see Downey U.S. Patent 2,627,477), which requires no alum.

Of course, in order to function properly and efiiciently to give increased dry strength, a material must be retained on the papermaking fibers and many such materials are dependent on alum for this. However, the dialdehydestarch ether reaction products of the present invention are adsorbed directly onto the cellulose fibers independently of alum and show good retention both with and without alum over the entire pH range (about 4-10) normally used in most papermaking processes. Furthermore the dialdehyde-starch ether reaction products of the present invention increase retention of paper additives on cellulose fibers. The dialdehyde-starch ether reaction products used in the present invention not only serve to give good sheet 8 formation, to give paper of increased dry strength and to retain paper additives, but said reaction products also serve in conjunction with size to give paper of increased ink resistance. If unmodified starch alone is used, it gives neither the desired dry strength nor the required retention of paper additives.

Thus, the dialdehyde-starch ether reaction products of the present invention may be used alone solely as such to give paper of increased dry strength and excellent formation, or they may be used in combination withone or more paper additives either at an acid, neutral or alkaline pH.

The dialdehyde-starch ether reaction products and the paper additives of the present invention may be added in a number of ways, as is well known in the art, e.g. as an aqueous solution or dispersion, or even in solid form provided they are uniformly mixed with the pulp slurry, and they may be added at any point before forming the Wet lap on the screen of the papermaking machine at any desired pH.

Although the examples hereinbefore show using clay and titanium dioxide as fillers, fillers in general are applicable in the present invention. Representative fillers include, for example, clay, calcium carbonate, magnesium carbonate, titanium dioxide and tale.

The amount of paper additive applicable in the present invention is not critical and will depend on a number of things well known in the art and may vary widely. For example the amount of paper additive in some cases will be about 0.01%-50%, but for most uses the amount will fall within the range of about 0.1%-20% by weight of the pulp on a dry basis. When dyes are the paper additive, the amount may be as low as about 0.001% but more often as low as about 0.01%.

As those skilled in this art will appreciate, there are applications where beating the pulp is unnecessary, and when heating is employed the extent of beating may vary considerably depending on the type pulp being used and the type paper being made. Beating to a Schopper-Riegler freeness of 850 cc.-300 cc. usually will be adequate for most purposes, freeness varying inversely with heating time. In the foregoing examples heating to a freeness of 820 cc. and 600 cc. was suflicient to give good results.

Although the starch ethers applicable herein are already in a gelatinized state, it does not harm to cook the dialdehyde-starch ether reaction products before using them. This was determined by repeating the examples hereinbefore except for cooking at C. for 15 minutes the aqueous dispersions of both the diethylaminoethyl hydroxypropyl starch and the dialdehyde-diethylaminoethyl hydroxypropyl starch reaction product before adding to the pulp slurry. The results with the cooked dispersions were substantially the same as with the uncooked. Some papermills may wish to use the dialdehydc-starch ether reaction products of the present invention in combination with other materials which require cooking. Also with respect to papermills which already have a cooker installed as part of the papermaking equipment, many of them cook such materials as a matter of practice.

As many apparent and Widely dilferent embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims.

What we claim and desire to protect by Letters Patent is:

1. Paper of excellent formation and superior dry strength containing uniformly distributed among the papermaking fibers thereof the reaction product of a dialdehyde and a gelatinized cationic-nonionic starch ether, said starch ether having the formula:

wherein X is starch, R is selected from the group consisting of alkylene and hydroxyalkylene, R and R are each selected from the group consisting of alkyl, aryl, aralkyl, cycloalkyl and heterocycloalkyl, and R is hydroxyalkyl, the amount of said reaction product being 0.001%% by dry weight basis of said papermaking fibers.

2. Product of claim 1 wherein the starch ether is a cationic-hydroxyalkyl starch ether.

3. Product of claim 1 wherein the starch ether is a dialkylaminoalkyl hydroxyalkyl starch ether.

4. Product of claim 1 wherein the starch ether is diethylaminoethyl hydroxypropyl starch.

5. Product of claim 1 wherein the dialdehyde is glyoxal and the starch ether is diethylaminoethyl hydroxypropyl starch.

6. Paper of excellent formation and superior dry strength containing uniformly distributed among the papermaking fibers thereof a paper additive and the reaction product of a dialdehyde and a gelatinized cationic-nonionic starch ether, said starch ether having the formula:

wherein X is starch, R is selected from the group consisting of alkylene and hydroxyalkylene, R and R are each selected from the group consisting of alkyl, aryl, aralkyl, cycloalkyl and heterocycloalkyl, and R is hydroxyalkyl, the amount of said reaction product being 0.001%10% by dry weight basis of said papermaking fibers.

7. Paper of excellent formation and superior dry strength containing uniformly distributed among the papermaking fibers thereof a size and the reaction product of a dialdehyde and a gelatinized cationic-nonionic starch ether, said starch ether having the formula:

wherein X is starch, R is selected from the group consisting of alkylene and hydroxyalkylene, R and R are each selected from the group consisting of alkyl, aryl, aralkyl, cycloalkyl and heterocycloalkyl, and R is hydroxyalkyl, the amount of said reaction product being 0.00l%10% by dry weight basis of said papermaking fibers.

8. Paper of excellent formation and superior dry strength containing uniformly distributed among the papermaking fibers thereof a filler and the reaction product of a dialdehyde and a gelatinized cationic-nonionic starch ether, said starch ether having the formula:

wherein X is starch, R is selected from the group consisting of alkylene and hydroxyalkylene, R and R are each selected from the group consisting of alkyl, aryl, aralkyl, cycloalkyl and heterocycloalkyl, and R is hydroxyalkyl,

10 the amount of said reaction product being 0.001%10% by dry weight basis of said papermaking fibers.

9. In a method of making paper comprising forming an aqueous slurry of a fibrous material, passing the slurry onto a screen and thereby forming a sheet of the fibrous material and causing most of the water to drain therefrom, and then pressing and drying the sheet to obtain the final paper product, the improvement which comprises adding to the slurry, prior to passing the slurry onto the screen, the reaction product of a dialdehyde and a gelatinized cationic-nonionic starch ether, said starch ether having the formula:

wherein X is starch, R is selected from the group consisting of alkylene and hydroxyalkylene, R and R are each selected from the group consisting of alkyl, aryl, aralkyl, cycloalkyl and heterocycloalkyl, and R is hydroxyalkyl, the amount of said reaction product being 0.001%10% by dry weight basis of said fibrous material.

10. In a method of making paper comprising forming an aqueous slurry of a fibrous material, passing the slurry onto a screen and thereby forming a sheet of the fibrous material and causing most of the water to drain therefrom, and then pressing and drying the sheet to obtain the final paper product, the improvement which comprises adding to the slurry, prior to passing the slurry onto the screen, a paper additive and the reaction product of a dialdehyde and a gelatinized cationic-nonionic starch ether, said starch ether having the formula:

R: wherein X is starch, R is selected from the group consisting of alkylene and hydroxyalkylene, R and R are each selected from the group consisting of alkyl, aryl, aralkyl, cycloalkyl and heterocycloalkyl, and R is hydroxyalkyl, the amount of said reaction product being 0.001%10% by dry weight basis of said fibrous material.

References Cited by the Examiner DONALL H. SYLVESTER, Primary Examiner. MORRIS O, WOLK, Examiner. 

1. PAPER EXCELLENT FORMATION AND SUPERIOR DRY STRENGTH CONTAINING UNIFORMLY DISTRUBUTED AMONG THE PAPERMAKING FIBERS THEREOF THE REACTION PRODUCT OF A DIALDEHYDE AND A GELATINIZED CATIONIC-NONIONIC STARCH ETHER, SAID STARCH ETHER HAVING THE FORMULA:
 9. IN A METHOD OF MAKING PAPER COMPRISING FORMING AN AQUEOUS SLURRY OF A FIBROUS MATERIAL, APSSING THE SLURRY ONTO A SCREEN AND THEREBY FORMING A SHEET OF THE FIBROUS MATERIAL AND CAUSING MOST OF THE WATER TO DRAIN THEREFROM, AND THEN PRESSING AND DRYING THE SHEET TO OBTAIN THE FINAL PAPER PRODUCT, THE IMPROVEMENT WHICH COMPRISES ADDING TO THE SLURRY, PRIOR TO PASSING THE SLURRY ONTO THE SCREEN, THE REACTION PRODUCT OF A DIALDEHYDE AND A GELATINIZED CATIONIC-NONIONIC STARCH ETHER, SAID STARCH ETHER HAVING THE FORMULA: 